An inkjet recording device provides energy by means of an energy providing unit such as a piezoelectric element that is provided at a liquid chamber in an ink head so as to eject ink in the liquid chamber from an ink nozzle as an ink droplet, and apply the ejected ink droplet onto recording paper to perform printing, which ink recording device is widely popular as it is cheap and compact. Below, a configuration of a related-art inkjet recording device is described with reference to the drawings.
FIG. 15 is a schematic configuration diagram illustrating a configuration of an ink supplying piping in the related-art inkjet recording device. As shown, the related-art ink supplying piping is configured to run from an ink cartridge 11 via a liquid sending pump 12 through a liquid sending tube 13 to a head tank 14, and a head is configured with single pipings of Bk, C, M, and Y. Then, when the ink within the head tank 14 is consumed for printing or maintenance, the ink is sent from the ink cartridge 11 by the liquid sending pump 12 through the liquid sending tube 13 into the head tank 14 to replenish the ink.
Now, there are three types of basic maintenance processes as follows:
1. Cleaning (Optional/Automatic): a light non-ejecting nozzle is recovered;
2. Refreshing (Optional): a non-ejecting nozzle not recovering with the cleaning is recovered; and
3. Atmospheric release filling (Automatic): if a negative pressure loss occurs, a negative pressure is generated.
While the above-described items 1 and 2 are nozzle recovery operations, so that a certain amount of ink needs to be discharged from the nozzle, as for the above-described item 3, from an objective of negative pressure generation (change in volume of the head tank), it is not necessary to discharge the ink from the nozzle.
FIG. 16 is a perspective view illustrating a structure of the head tank of the inkjet recording device. As shown, a negative pressure lever 14-1, which is provided inside the head tank, is a lever which operates following a film 14-2 which is displaced in accordance with an amount of consumption of ink contained within a head tank in which the negative pressure is occurring due to a spring (not shown) which biases the film 14-2. A supply port 14-3 is a supply port into which ink is supplied from below-described ink cartridges 110k-110y of FIGS. 1 and 3 via an ink supply tube 136 of FIG. 3. Moreover, an atmospheric release pin 14-4 is a pin which releases the inside of the head tank to the atmospheric state, as needed. Furthermore, below the head tank is provided a recording head 14-5 which injects an ink droplet. Moreover, a sensing mechanism 14-6 which senses the ink or air is provided.
Then, as shown in FIG. 17, for generating the negative pressure within the head tank, the ink is discharged from a head nozzle 15 by an absorption cap 21 which covers the head nozzle 15 to change the volume within the head tank 14 to deform a spring inside the head tank. The ink discharged from the head nozzle 15 by the absorption cap 21 is stored as waste liquid at a waste liquid tank 23 by an absorption pump 22.
On the other hand, in these inkjet recording devices, it is becoming predominant to use an ink cartridge as a unit for supplying ink. There is a problem that a non-ejecting of the ink is caused by air mixing in when the ink cartridge is replaced. There have been a number of related-art proposals made in order to overcome this problem. As one of the proposals, Patent document 1 discloses a liquid ejecting device which is provided with an ink supply conduit which supplies ink from an ink tank to an ink head, and an ink flux conduit which refluxes the ink from the ink head to the ink tank to circulate the ink between the ink head and the ink tank to prevent the ink from leaking from a nozzle. For ink-supplying piping components in the related art inkjet recording devices including what is disclosed in Patent document 1, an ink cartridge, a liquid sending pump, a liquid sending tube, a head tank, and an ink head use a lot of resin material for an ink flow channel section. Moreover, for a joint between parts, a rubber packing, etc. is used to ensure sealing performance. At the body waiting time, inside the head tank is in a state of negative pressure. There is no problem as long as the body waiting time is a waiting time at a level expected in normal use.
Moreover, in an inkjet recording device with the ink cartridge having a large ink capacity, the ink cartridge being directly mounted to a recording head which is mounted to a carriage and ink being supplied to the recording head could cause trouble with carriage operations due to the weight of the ink cartridge, thus decreasing the image quality. Then, there is an inkjet recording device which has provided therewith the ink cartridge on the body side and which has a recording head within a carriage, provided with a head tank 14, as shown in FIG. 14, which temporarily stores the ink to be used in printing. In such an inkjet recording device as described above, when trying to send the ink with the ink cartridge on the body side being empty, the negative pressure within a liquid sending channel from the cartridge on the body side to the head tank becomes strong, so that an air bubble gets into the ink sending channel by tucking in and taking out the ink cartridge. When the air bubble gets into the liquid sending flow channel, it gets into a subtank via the liquid sending channel. Then, if ink is supplied with an atmospheric release valve being open, for example, a mixture of the air bubble and the ink could leak from the atmospheric release valve. The mixture leaking from the atmospheric release valve leads to a failure such as a head damage. Moreover, the air bubble which found its way into the mixture penetrating into the nozzle in the recording head leads to an image degradation defect such as a nozzle clog, etc.
Then, in order to solve the above-described problems, a number of proposals have been made to date. As one of the proposals, Patent document 2 discloses an inkjet printer which is provided with an intermediate ink tank between an ink cartridge and a recording head, and with a pressure sensor remote from the intermediate ink tank to sense a negative pressure state within the recording head, and move the intermediate ink tank upward and downward as needed to maintain a desired negative pressure. Moreover, Patent document 3 discloses a proposed ink supply device in which, when a pressure of a main tank chamber decreases as ink is consumed, the ink for an amount corresponding to the decreased pressure is automatically supplied from a sub tank chamber having meniscus constituting members that accompanies the main tank chamber for storing the ink so as to maintain a desired negative pressure. Furthermore, Patent document 4 discloses a proposed inkjet pen in which the ink is filled into a sealed up ink tank, one end of which is provided with a small hole being released to the atmosphere, and, when the ink within the ink tank is consumed, air is supplied via the small hole into the ink tank, which inside is maintained at a desired negative pressure.